Updated description of nowrap command

Synced the description comment with the command.
Assumed comment was wrong instead of the command.
No offense, but isn't `set wrap` more comfortable? :)
Add `<leader>gw :Gwrite<CR>` mapping to Readme
Merge pull request #469 from swapnilmj/3.0

Updated description of nowrap command
Update README.markdown

fixed typo (or perhaps changed syntax) for Surround quick help
Merge pull request #485 from aauthor/sd-typo_fix

Update README.markdown